This is so true. We just had a request on pygtk-list. Is this just a matter of
styling, or is code changing required here?

Is this the same thing as bug #106406?

Hard to say. Your bug is confusing because there seem to be requests for lines
of two different types there (both expander connectors and table grid lines),
and this one is more specific, relating only to expander connectors.

can or should this be done at the theme engine level? If so are there any  
engines which do draw these connecting lines and boxes?  
  
i would consider writing such an engine.  
  
in the meantime i have to use the old deprecated widgets.  

I originally designed it such that you could draw in the lines, but that code
got dropped along the way.  You'd have to make some changes to gtktreeview.c to
get it working and add a style property so that themes could turn it on.  I
don't think that it's fundamentally a lot of work though -- most of the
information needed at each row is available.  It's mostly a matter of writing
the drawing code.

thanks Jonathan. 
 
i'm not confident enough yet, personally, to add code to gtk itself. Perhaps 
later. 
 
but do you know if there is any antipathy towards this, what is after all a 
fairly ubiquitous feature? Especially as it was in gtk1.2. 

It's not a developer-driven feature, but rather a theme feature. Since the
TreeView was complicated enough, we only wrote the default behavior that we want
(since all those lines tends to confuse people).

*** Bug 305842 has been marked as a duplicate of this bug. ***

I also would like to have this feature present.
MAybe make it so that it has to be turned one by a rc option so it can be used
in themes and let the normal connectorless version be the default.

And as for confusing people. Some find the connector less version much more
confusing then the connected. Especialy in long lists.

See attached screenshot of what i would like to do.

Created attachment 52571 [details]
treeview connector lines

The expander can be themed these days.  And with 2.10 you can turn on "tree lines" with a property.  This is not a style property though.

Matthias, do you need we need some changes here before we release 2.10?

No, I don't think so. 
It is not clear to me if tree lines should be a style property.
You clearly don't want to have them on every tree, and thus the
app needs some way to indicate that tree lines are suitable for
a given tree view. A property seems a fine way to do that.

Okay, I guess we can close this bug now then?  Since we support everything and you were the original reporter ;)